Abstract: Recent results from the Pierre Auger Collaboration have shown that the
composition of ultrahigh-energy cosmic rays (UHECRs) becomes gradually heavier
with increasing energy. Although gamma-ray bursts (GRBs) have been promising
sources of UHECRs, it is still unclear whether they can account for the Auger
results because of their unknown nuclear composition of ejected UHECRs. In this
work, we revisit the possibility that low-luminosity GRBs (LL GRBs) act as the
sources of UHECR nuclei, and give new predictions based on the intrajet nuclear
composition models considering progenitor dependencies. We find that the
nuclear component in the jet can be divided into two groups according to the
mass fraction of silicon nuclei, Si-free and Si-rich. Motivated by the
connection between LL GRBs and transrelativistic supernovae, we also consider
the hypernova ejecta composition. Then, we discuss the survivability of UHECR
nuclei in the jet base and internal shocks of the jets, and show that it is
easier for nuclei to survive for typical LL GRBs. Finally, we numerically
propagate UHECR nuclei ejected from LL GRBs with different composition models
and compare the resulting spectra and composition to Auger data. Our results
show that both the Si-rich progenitor and hypernova ejecta models match the
Auger data well, while the Si-free progenitor models have more difficulty in
fitting the spectrum. We argue that our model is consistent with the newly
reported cross correlation between the UHECRs and starburst galaxies, since
both LL GRBs and hypernovae are expected to be tracers of the star-formation
activity. LL GRBs have also been suggested as the dominant origin of IceCube
neutrinos in the PeV range, and the LL GRB origin of UHECRs can be critically
tested by near-future multimessenger observations.

Comments:

17 pages, 16 figures, minor corrections, added the discussion about the possible correlation with starburst galaxies, version accepted by PRD